Breaking News
Comments
Newest First | Oldest First | Threaded View
Garcia-Lasheras
User Rank
Author
Re: Interesting, But Not Quite
Garcia-Lasheras   2/19/2014 5:38:02 PM
NO RATINGS
@HankWalker: I'm glad to hear some comments from an old-school Caltech student. Today, this institution continues the leading research in asynchronous logic with people such as Alain Martin -- I know he is not a youngster, but still kicking ;-)

About your comments, I totally agree with your explanation about throughput. In addition to the classic laundry example, that explains the case for a straight-forward pipeline, we should consider that micropipes can be used in more complex designs including fork and funnel structures. e.g. if they are applied to a pipelined processor in which the ALU includes different ops, each one with different processing times, the throughput has the potential of being higher than the synchronous counterpart depending on the instructions distribution and order.

In addition, when applying delay insensitive or quasi-delay insensitive approaches to designing micropipes, we can actually reach higher throughputs as we don't need to make any worst-case timing assumption based on process/temperature/voltage variations: they just run as fast as they can -- of course, we could theoretically run a faster synchronous pipe when full data load, but in practice we would face very important clock issues when calculating the optimal period.

About GALS, by following the included link, you'll find a previous blog covering the clocking issues that lead to this compromise solution (synchronous islands plus asynchronous network-on-chip communications).

Finally, about the elastic/inelastic classification, I've directly taken it from Ivan's ACM Turing's Award lecture -- the blog includes the link to this precious gem too. Quoting him:

"Some pipelines are inelastic; the amount of data in them is fixed. The input rate and the output rate of an inelastic pipeline must match exactly. Stripped of any processing logic, an inelastic pipeline acts like a shift register. Other pipelines are elastic; the amount of data in them may vary. The input rate and the output rate of an elastic pipeline may differ momentarily because of internal buffering."

 

HankWalker
User Rank
Author
Interesting, But Not Quite
HankWalker   2/19/2014 12:59:46 PM
NO RATINGS
Ivan was starting to cover this material when I was an undergrad at Caltech in the late 1970s. The micropipeline throughput is still limited to the same speed as the synchronous pipe, since they are both limited by the slowest stage. Consider a washer and dryer. You can pile up wet laundry on top of the dryer (micropipe), but it will still have to wait for the dryer. What the micropipe does provide is elastic buffering if the pipe input load is bursty, achieving higher throughput since the pipe source will not have to stall.

You have not discussed micropipe disadvantages. The loopback time of request/ack signaling adds a stage delay overhead that is not present in a synchronous clock design, so the synch pipe can potentially have a shorter cycle time. But this must be balanced against the effort (power/area) required to distribute a synch clock. This is why GALS is proposed - a synch clock is better over small regions and asynch over larger regions.

I think "elastic FIFO" is a redundant term. A FIFO that is not elastic is pointless.

 



Datasheets.com Parts Search

185 million searchable parts
(please enter a part number or hit search to begin)
Radio
LATEST ARCHIVED BROADCAST

What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.

Brought to you by:

Most Recent Comments
rick merritt
 
Saturation
 
DCH0
 
realjjj
 
traneus
 
realjjj
 
realjjj
 
Doug_S
 
spike_johan
Like Us on Facebook
Special Video Section
Once the base layer of a design has been taped out, making ...
In this short video we show an LED light demo to ...
The LTC2380-24 is a versatile 24-bit SAR ADC that combines ...
In this short video we show an LED light demo to ...
02:46
Wireless Power enables applications where it is difficult ...
07:41
LEDs are being used in current luxury model automotive ...
With design sizes expected to increase by 5X through 2020, ...
01:48
Linear Technology’s LT8330 and LT8331, two Low Quiescent ...
The quality and reliability of Mill-Max's two-piece ...
LED lighting is an important feature in today’s and future ...
05:27
The LT8602 has two high voltage buck regulators with an ...
05:18
Silego Technology’s highly versatile Mixed-signal GreenPAK ...
The quality and reliability of Mill-Max's two-piece ...
01:34
Why the multicopter? It has every thing in it. 58 of ...
Security is important in all parts of the IoT chain, ...
Infineon explains their philosophy and why the multicopter ...
The LTC4282 Hot SwapTM controller allows a board to be ...
This video highlights the Zynq® UltraScale+™ MPSoC, and sho...
Homeowners may soon be able to store the energy generated ...
The LTC®6363 is a low power, low noise, fully differential ...